The present invention relates to sensor methods and systems. The present invention also relates to sensors that measure the turbidity and quality of fluid having particulate content therein. The present invention also relates to semiconductor-based sensors. The present invention additionally relates to photodiode-based sensors and methods thereof. The present invention also relates to laser emitting sensor devices and methods thereof. The present invention relates to turbidity sensors that monitor the status of a fluid and determine the presence or level of impurities in the fluid. The present invention also relates to techniques for measuring very low concentrations of particles in fluids.
Reducing the amount of energy consumed by a machine for cleansing articles, such as a clothes washer, is a significant problem. In such a machine, the amount of energy consumed is primarily determined by the amount of energy needed to heat the liquid, such as water, used to cleanse the articles. Thus, decreased liquid consumption for such machines may result in a significant improvement in energy efficiency.
Appliances for cleansing articles, such as clothes washers, are typically preprogrammed to perform a complete washing in a predetermined number of wash cycles, each wash cycle having a predetermined duration. A wash cycle may provide substantially particle-free liquid to the machine, circulating the liquid during the wash cycle, and draining or flushing the liquid from the machine after being used to wash or cleanse the articles. Often the machine user may select from a limited number of preprogrammed options. Such preprogramming does not use energy efficiently because the machine may either perform an excessive number of wash cycles, or perform each cycle for an excessive duration, to assure that cleanliness of the articles is achieved. To improve the energy efficiency of such appliances, closed loop feedback control systems can be incorporated into the washing machine. Several techniques have been utilized to indirectly monitor cleanliness of the articles during closed loop feedback control of the appliance, including use of a device for measuring the turbidity of the liquid used to wash the articles.
Devices for measuring turbidity that detect the transmission of light propagated through water used to wash the articles have been employed to ascertain information about progress of the wash. However, such devices have not been ideal for use in household appliances. Such devices are oftentimes difficult or non-economic to implement due to the electronic circuitry necessary to perform the complex turbidity measurements. Furthermore, such devices are subject to measurement error. Factors such as water turbulence, cloudiness of the water sample chamber, light source dimming, or device performance degradation may cause attenuation of the amount of light detected and thus affect measurement accuracy. The precision of such devices is also not entirely satisfactory. This imprecision has the additional effect of making turbidity measurements provided by such devices difficult to interpret in a closed loop feedback control system.
Manufacturers of washing machines thus desire to control the washing algorithms with such machines in order to maintain high washability standards and increase energy efficiency. Turbidity measurement must be accurate over a broad range of washing cycles and turbid environments in order to make proper decisions during washing cycles.
Turbidity sensors can be utilized to monitor turbidity in liquids operating within turbid environments, such as a washing machine. Turbidity sensors monitor the status of a fluid and, more particularly, determine the presence or level of impurities in the fluid. Often the presence of impurities determines the suitability of the fluid for use in its intended purpose. As an example, lubricating oil having too high a contamination level should be cleansed or changed.
Turbidity sensors are thus utilized in many different types of applications, for example, in association with machines for washing articles, such as dishwashers and washing machines. Most turbidity sensors measure the effect on a light beam of particulate matter suspended within a fluid. Some turbidity sensors utilize only a transmitted light signal, while others utilize both scattered and transmitted light.
Certain prior art turbidity sensors operate by shining a light into a test cell that contains the fluid under scrutiny. The degree to which the light is transmitted as well as scattered gives an indication of the turbidity or pureness of the fluid sample. The previously known turbidity sensors often use light emitting diodes (LEDs) for light sources and the use of photodiodes and phototransistors for use as detectors to reduce costs. An output from such systems may employ light intensity to frequency converters. For example, a photodiode or phototransistor that monitors light intensity is coupled to such a converter to generate a signal whose frequency corresponds to and varies with the turbidity level of the fluid.
A problem identified in prior art turbidity sensors is that the light source that shines light into the fluid sample can change its emission characteristics with time or with variations in temperature. Similarly, changes in operating characteristics can take place in the sensors that are used to sense the light that travels through the fluid.
Prior art turbidity sensors have experienced problems when trying to sense the condition of fluids that are either at low or high turbidity levels. In addition, the sensor""s test cell must be large enough to pass all suspended particles in the test material without fouling. The test cell must also be small enough, however, to allow light to be transmitted through the cell and received by a sensor on the opposite side of the test cell from the source. At high turbidity levels, a long transmission path will not pass enough light to allow the sensor to provide a meaningful measurement as the variation in light output such as a frequency. Conversely, at low turbidity levels, a test cell""s transmission path may be too short to allow sufficient light to be scattered or absorbed to produce a meaningful measurement. The use of such test cells or sample cells is thus inefficient and difficult to implement.
Many fluid filters for liquids and gases function by particle entrapment. As filters gradually become clogged by the particles, detection of the need for cleaning or replacement is often accomplished by mass air flow measurements downstream of the filter, pressure drop measurements across the filter and motor or pump loading. All of these techniques have disadvantages in terms of cost, accuracy or reliability.
In addition, the structure and assembly of previously known turbidity sensors is often complex, particularly where the structure supports for the components are arranged to avoid improper alignments of the components with respect to each other. As a result, any supports for the components that are adjustable so as to permit a final alignment of the parts after assembly are quite complex and costly. Moreover, the previously known components and the support structures for the components are not well adapted for simple and economical mass production, and the assembly of products employing turbidity sensors that otherwise would be readily mass produced can be substantially complicated by installation of the previously known support structures and component assemblies. In addition, the performance of systems using light sensors can be substantially affected by temperature changes and component changes due to aging, contamination and the like.
The incorporation of turbidity sensors into a machine for washing articles, such as a washing machine or dishwasher, can increase the cost of the machine by a significant amount because of the complexity of such known turbidity sensors. Typically, a turbidity sensor can include a microprocessor, which controls the operation of the turbidity sensor and analyzes the signals received thereby to determine the magnitude of turbidity of the water within the machine for washing articles. It would be beneficial if the operation of a turbidity sensor could be significantly simplified and, as a result, the costs of the turbidity sensor significantly reduced.
One beneficial use to which a turbidity sensor can be applied is the conservation of water during the operation of a machine for washing articles. The repeated draining and refilling of a machine for washing articles uses a significant amount of water and, if it is not excessively dirty, the draining of the water can represent a significant waste of water. The appropriate use of a turbidity sensor can avoid the unnecessary draining and refilling of machines for washing articles.
There does not currently exist a low-cost method and device for sensing turbidity needed to measure very low concentrations of particulate in translucent fluids. In addition to utilizing turbidity sensors to assist in conserving water in devices such as washing machines, it is often necessary to measure extremely low levels of contaminants in water purification systems, hydraulic fluids, oils or other translucent fluids. In washing machines, for example, it is desirable to measure particles of extremely small size, such as dissolved starch, that have poor light-scattering properties. Such particles go undetected by current commercial methods of turbidity sensing, including devices and systems thereof.
A need thus exists for a device, including systems and methods thereof, for measuring turbidity in a simple and economic manner and which overcomes the aforementioned problems associated with prior art turbidity sensors. A need particularly exists for a turbidity sensor that overcomes the inability of prior art turbidity sensors to efficiently detect extremely low levels of particles in fluids. A low-cost sensing of turbidity is needed in a machine for washing articles where a full range of particulate content must be measured. In addition, accurate measurement of turbidity is needed in other applications, such as water quality systems, hydraulic oils, or any other application where fluid quality is measured.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is one aspect of the present invention to provide sensor methods and systems.
It is another aspect of the present invention to provide a sensor that measures the turbidity and quality of fluids and viscous environments having particulate content.
It is also an aspect of the present invention to provide a semiconductor-based sensor.
It is an additional aspect of the present invention to provide photodiode-based sensor methods and systems.
It is another aspect of the present invention to provide laser emitting sensor devices and methods thereof.
It is still another aspect of the present invention to provide turbidity sensors that monitor the status of a fluid and determine the presence or level of impurities in the fluid.
It is yet another aspect of the present invention to provide techniques for measuring very low concentrations of particles in fluids.
The above and other aspects are achieved as is now described. A turbidity sensor apparatus and method for measuring very low concentrations of particles in a fluid are disclosed herein. The turbidity sensor is generally composed of a laser light source for emitting laser light through a fluid. Such a fluid may be hydraulic fluid, oil, water utilized in water purification systems, or other translucent fluids. The turbidity sensor includes a first light-sensitive detector located 90 degrees to incident laser light emitted from the laser light source and a second light-sensitive detector located at an obtuse angle to the incident laser light emitted from the laser light source, wherein the first and second light-sensitive detectors respectively measure side scattered light and forward scattered light reflected from particles contained within the fluid that come into contact with laser light emitted from the laser light source, thereby providing an accurate and reliable measurement of very low concentrations of particles within the fluid. The turbidity sensor also includes a component for capturing incident laser light entirely emitted from the laser light source, thereby preventing reflection of the laser light back into the fluid. The laser light source may be a Vertical Cavity Surface Emitting Laser (VCSEL) or other light emitting light source.